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      Heme oxygenase-1 and its metabolites affect pancreatic tumor growth in vivo

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          Abstract

          Background

          Pancreatic cancer (PaCa) is a fatal human cancer due to its exceptional resistance to all current anticancer therapies. The cytoprotective enzyme heme oxygenase-1 (HO-1) is significantly overexpressed in PaCa and seems to play an important role in cancer resistance to anticancer treatment. The inhibition of HO-1 sensitized PaCa cells to chemo- and radiotherapy in vitro.

          Therefore, we investigated the effects of HO-1 and its metabolites biliverdin, carbon monoxide and iron on PaCa cells.

          PaCa cell lines with divergent HO-1 expression patterns were used in a murine orthotopic cancer model. HO-1 expression and activity was regulated by zinc (inhibition) and cobalt (induction) protoporphyrin. Furthermore, the influence of cellular HO-1 levels and its metabolites on effects of standard chemotherapy with gemcitabine was tested in vivo and in vitro.

          Results

          High HO-1 expression in PaCa cell lines was associated with increased chemoresistance in vitro. Chemoresistance to gemcitabine was increased during HO-1 induction in PaCa cells expressing low levels of HO-1. The inhibition of HO-1 activity in pancreatic tumors with high HO-1 boosted chemotherapeutic effects in vivo significantly. Furthermore, biliverdin and iron promoted PaCa resistance to chemotherapy. Consequently, specific iron chelation by desferrioxamine revealed profound anticancerous effects.

          Conclusion

          In summary, the inhibition of HO-1 and the chelation of iron in PaCa cells were associated with increased sensitivity and susceptibility of pancreatic tumors to chemotherapy in vivo. The metabolites biliverdin and iron seem to be involved in HO-1-mediated resistance to anticancer treatment. Therefore, HO-1 inhibition or direct interference with its metabolites may evolve new PaCa treatment strategies.

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          Most cited references46

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          Carbon monoxide has anti-inflammatory effects involving the mitogen-activated protein kinase pathway.

          The stress-inducible protein heme oxygenase-1 provides protection against oxidative stress. The anti-inflammatory properties of heme oxygenase-1 may serve as a basis for this cytoprotection. We demonstrate here that carbon monoxide, a by-product of heme catabolism by heme oxygenase, mediates potent anti-inflammatory effects. Both in vivo and in vitro, carbon monoxide at low concentrations differentially and selectively inhibited the expression of lipopolysaccharide-induced pro-inflammatory cytokines tumor necrosis factor-alpha, interleukin-1beta, and macrophage inflammatory protein-1beta and increased the lipopolysaccharide-induced expression of the anti-inflammatory cytokine interleukin-10. Carbon monoxide mediated these anti-inflammatory effects not through a guanylyl cyclase-cGMP or nitric oxide pathway, but instead through a pathway involving the mitogen-activated protein kinases. These data indicate the possibility that carbon monoxide may have an important protective function in inflammatory disease states and thus has potential therapeutic uses.
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            Heme oxygenase-1: unleashing the protective properties of heme.

            Heme oxygenase (HO)-1 catabolizes heme into three products: carbon monoxide (CO), biliverdin (which is rapidly converted to bilirubin) and free iron (which leads to the induction of ferritin, an iron-binding protein). HO-1 serves as a "protective" gene by virtue of the anti-inflammatory, anti-apoptotic and anti-proliferative actions of one or more of these three products. Administration of CO, biliverdin, bilirubin or iron-binding compounds is protective in rodent disease models of ischemia-reperfusion injury, allograft and xenograft survival, intimal hyperplasia following balloon injury or as seen in chronic graft rejection and others. We suggest that the products of HO-1 action could be valuable therapeutic agents and speculate that HO-1 functions as a "therapeutic funnel", mediating the beneficial effects attributed to other molecules, such as interleukin-10 (IL-10), inducible nitric oxide synthase (NOS2; iNOS) and prostaglandins. This Review is the third in a series on the regulation of the immune system by metabolic pathways.
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              Heme oxygenase-1 mediates the anti-inflammatory effect of interleukin-10 in mice.

              The mechanisms underlying the action of the potent anti-inflammatory interleukin-10 (IL-10) are poorly understood. Here we show that, in murine macrophages, IL-10 induces expression of heme oxygenase-1 (HO-1), a stress-inducible protein with potential anti-inflammatory effect, via a p38 mitogen-activated protein kinase-dependent pathway. Inhibition of HO-1 protein synthesis or activity significantly reversed the inhibitory effect of IL-10 on production of tumor necrosis factor-alpha induced by lipopolysaccharide (LPS). Additional experiments revealed the involvement of carbon monoxide, one of the products of HO-1-mediated heme degradation, in the anti-inflammatory effect of IL-10 in vitro. Induction of HO-1 by IL-10 was also evident in vivo. IL-10-mediated protection against LPS-induced septic shock in mice was significantly attenuated by cotreatment with the HO inhibitor, zinc protoporphyrin. The identification of HO-1 as a downstream effector of IL-10 provides new possibilities for improved therapeutic approaches for treating inflammatory diseases.
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                Author and article information

                Journal
                Mol Cancer
                Molecular Cancer
                BioMed Central
                1476-4598
                2009
                9 June 2009
                : 8
                : 37
                Affiliations
                [1 ]Department of Surgery, Technische Universität München, Munich, Germany
                [2 ]Department of Surgery, University of Heidelberg, Heidelberg, Germany
                [3 ]Institute of Immunology, University of Heidelberg, Heidelberg, Germany
                Article
                1476-4598-8-37
                10.1186/1476-4598-8-37
                2702301
                19508729
                1d67bf94-ac80-4bf7-9fe5-a8207493615e
                Copyright © 2009 Nuhn et al; licensee BioMed Central Ltd.

                This is an Open Access article distributed under the terms of the Creative Commons Attribution License ( http://creativecommons.org/licenses/by/2.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

                History
                : 25 November 2008
                : 9 June 2009
                Categories
                Research

                Oncology & Radiotherapy
                Oncology & Radiotherapy

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